The goal in this second revision of our grant is to increase our understanding of the development of very low birth weight (VLBW) children by examining whether five different mutual regulatory (MR) processes observed during a joint play session between mothers and their VLBW (< 1600g) or healthy, term (FT) children at 1 1/2 and 2 1/2 years post term mediate the relation between children's biologic or social risk status and their developmental and behavioral outcomes at 2 1/2 years. Other goals are to evaluate the extent to which VLBW status, co-morbid medical risk, social risk, child gender, and their interactions are related to these MR processes at each age and longitudinally, and to evaluate the stability of MR processes during this time period. Using a microanalytic, computerized scoring system (Child and Caregiver Mutual Regulation System, CCMR), we will code maternal and child affect and behavior from videotapes of the joint play session at each age. Five MR variables (dyadic affect sharing, reparation, synchrony, bi-directionality, and maternal regulatory responsiveness) will be generated using time series analysis and sequential data analytic techniques. The videotapes of the joint play sessions have already been collected as part of a self-funded extension of a larger and completed study of the effect of Neonatal White Matter Disorder (NWMD) on infant neuromotor development from birth to 1 1/2 years post term (RO1 NS33002-01A2, E. Tronick, PI). Using our own funds, we followed 83 (95%) dyads to 2 1/2 years post term. The proposed analyses will be based on the 88 dyads (62% boys, 53% VLBW) that participated in either the lY2 or the 21/2-year visit. At each visit, children's developmental and behavioral functioning (BSID-II MDI & PDI, BRS, language skills) was evaluated, and mothers provided information about demographics, their child's functioning, and their own adaptation. Findings will provide novel information about individual differences in the mother-child relationship in the VLBW population and shed further light on how mother-child interactive processes may mediate the relation between VLBW/medical risk and children's developmental and behavioral outcomes. This information will enhance our ability to design and implement effective prevention and intervention services for VLBW children and their families.